Rotation detector

ABSTRACT

Even when a cheap magnetic responsive element is used for a magnetic detecting portion, a rotation detector excellent in vibration resistance is provided, a housing  1  being provided with a tubular insertion portion  1   a  through which an axle  13  is inserted. A rotor  5  is provided with a cylindrical portion  5   a  through which the insertion portion  1   a  is inserted and that has a plurality of magnetic poles and rotates synchronously with a front wheel (wheel)  11  fitted to the axle  13 . The magnetic detecting portion (rotation detecting portion)  3  detects a change of magnetic poles accompanying the rotation of the cylindrical portion  5   a . A spacer (magnetic member)  4  is disposed in the surroundings of the insertion portion  1   a  of a bottom portion  1   g  of the housing 1, and holds the rotor 5 at the bottom portion  1   g  when the cylindrical portion  5   a  is fitted into the insertion portion  1   a.

TECHNICAL FIELD

[0001] The present invention relates to a rotation detector that isattached to a hub of a front wheel of a two-wheeled vehicle, such as amotorcycle, a bicycle and so on, and transmits the rotation number of awheel of the two-wheeled vehicle to a indicator such as a speed meterand so on.

BACKGROUND ART

[0002] As an existing electric rotation detector, there is one such asdisclosed in Japanese Patent Laid-Open No. 264817/1990. When such therotation detector is used as a rotation detector for use in atwo-wheeled vehicle (for instance, a motorcycle), the rotation detectoris formed by disposing a magnetic detecting element (Hall IC) and amagnet, both of which are mounted on a circuit board, to a substantiallycylindrical resin case having a detection surface for detecting adetecting object so as to follow the detection surface, and followed bysealing the circuit board, the magnetic converting element and themagnet with a sealing member made of an epoxy resin and so on. It isgeneral for the rotation detector to be attached to a mission case or asprocket cover and to detect, as a detecting object, a mission gear, atooth point of the sprocket or the like revolving therein.

[0003] When a tooth point of a mission gear or sprocket or the like isdetected with such the rotation detector as a detecting object, sincethere is a little clearance in the detecting object, the object iscaused to vibrate owing to a body stiffness, an engine displacement orthe like of a vehicle (two-wheeled vehicle), and a detection positiongap between the detecting object and the rotation detector may result influctuating. This generates a magnetic fluctuation in the rotationdetector and resultantly becomes detection noise. Accordingly, there isa problem in that an indicator for displaying, for instance, a speedcorresponding to an output data that is output from the rotationdetector may wrongly operate.

[0004] The present inventors paid attention to the above problem andhave proposed, as shown in Japanese Patent Laid-Open No. 229714/1997, anelectric rotation detector that can be attached to a hub of a frontwheel of a two-wheeled vehicle. The rotation detector is provided to aresin housing with an insertion portion through which an axle (frontaxle) of a two-wheeled vehicle is inserted, is equipped to the insertionportion with a rotor having a plurality of magnetic poles that rotatessynchronously with a wheel fitted to the axle, and detects the rotationof the rotor by means of a magnetic detecting portion that isaccommodated in the housing and made of such as Hall IC or the like. Therotation detector, without incurring an adverse influence of thedetection noise due to the vibration of the detecting object, allowsaccurately detecting the rotation.

[0005] In recent years, demands for the cost reduction of the rotationdetectors that are applied to the two-wheeled vehicles are increasing.Accordingly, there is a tendency in which the rotation detectingportions are switched from the magnetic detecting elements such as HallICs and so on to cheaper magnetic responsive elements such as reedswitches or the like. However, there is a problem in the magneticdetecting means using the magnetic responsive element in that from itcharacteristics and structure, in comparison with the magnetic detectingportion that uses the Hall IC or the like, vibration resistance is low.

[0006] The invention is carried out by paying attention to theaforementioned problem and intends to provide a rotation detector thatis excellent in the vibration resistance even when the cheaper magneticresponsive element is used in the magnetic detecting portion.

DISCLOSURE OF THE INVENTION

[0007] In the invention, in order to overcome the aforementionedproblem, a rotation detector comprises a housing provided with a tubularinsertion portion through which an axle is inserted; a rotor that isprovided with a cylindrical portion through which the insertion portionis inserted and has a plurality of magnetic poles, and rotatessynchronously with a wheel that is fitted to the axle; a rotationdetecting portion for detecting a change of the magnetic polesaccompanying the rotation of the cylindrical portion; and a magneticmember that is disposed in the surroundings of the insertion portion ofa bottom of the housing and can hold the rotor to the bottom when thecylindrical portion is fitted into the insertion portion.

[0008] In addition, the magnetic member is formed of a plane tablemember disposed so as to surround the insertion portion in the bottomportion of the housing.

[0009] Furthermore, the magnetic member is formed integrally with theinsertion portion.

[0010] Still furthermore, a rotation detector comprises a housing oneend of which abuts against an inner wheel of a bearing that is disposedto a hub of a wheel, and which is provided with a tubular insertionportion through which an axle that penetrates through the bearing isinserted; a rotor that is provided with a cylindrical portion, throughwhich the insertion portion is inserted, and a rotation transmitter forrotating the cylindrical portion synchronously with the rotation of thewheel; a rotation detecting portion that is disposed in the housing anddetects the rotation of the rotor; and a convexity that is disposed at aposition that faces the inner wheel in the bearing of the rotor andcapable of abutting against the inner wheel.

[0011] Furthermore, the convexities are partially disposed at positionsthat face the inner wheel and along a periphery of an opening throughwhich the insertion portion is inserted.

[0012] Furthermore, a rotation detector comprises a housing one end ofwhich abuts against a bearing that is disposed to a hub of a wheel, andwhich is provided with a tubular insertion portion through which an axlethat penetrates through the bearing is inserted; a rotor that isprovided with a cylindrical portion, through which the insertion portionis inserted, and a rotation transmitter for transmitting the rotation ofthe wheel to the cylindrical portion by abutting against arotation-biasing portion disposed to the hub; a rotation detectingportion that is disposed in the housing and detects the rotation of therotor; and a contact portion that is disposed in a portion that abutsagainst the rotation-biasing portion of the rotation transmitter andmaintains a contact area between both members smaller.

[0013] Furthermore, the contact portion is provided with a projectionthat comes into contact with a flat surface of the rotation-biasingportion.

[0014] Still furthermore, the contact portion is made of a flat surfacethat comes into contact with the projection disposed to therotation-biasing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is an exploded perspective view of a first embodiment ofthe invention;

[0016]FIG. 2 is a substantial sectional view of the first embodiment;

[0017]FIG. 3 is a plan view of a housing of the first embodiment;

[0018]FIG. 4 is a diagram showing an attached state in the firstembodiment;

[0019]FIG. 5 is a substantial sectional view showing a modification ofthe first embodiment;

[0020]FIG. 6 is a substantial sectional view of a second embodiment;

[0021]FIG. 7 is a diagram showing an attached state in the secondembodiment;

[0022]FIG. 8 is a substantial sectional view showing a modification ofthe second embodiment;

[0023]FIG. 9 is an exploded perspective view of a third embodiment; and

[0024]FIG. 10 is a diagram showing relationship between a rotor and ahub in the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] In the following, a first embodiment of the invention will beexplained with reference to the accompanying drawings. In FIGS. 1through 3, a rotation detector A is constituted of a housing 1, acircuit board 2, a magnetic detecting portion (rotation detectingportion) 3, a spacer (magnetic member) 4, a rotor 5, a sealing member 6and a wiring cord 7.

[0026] The housing 1 is made of a resin material such as polybutyleneterephthalate, nylon or the like. In a substantial center of the housing1, a cylindrical insertion portion 1 a that is made of a metal andthrough which an axle, which will be explained later, is inserted isinsertion molded, and outside of the insertion portion 1 a anaccommodating space 1 b for disposing a rotor 5, which will be explainedlater, rotatably with respect to an outer periphery of the insertionportion 1 a. Furthermore, along a periphery of a place where the rotor5, which will be explained later, is disposed to the insertion portion 1a in the accommodating space 1 b, a wall portion 1 c is formedsurrounding the rotor 5, and between the wall portion 1 c and the rotor5 fitted into the insertion portion 1 a a lubricant 8 made of grease orthe like is coated. In addition, at a predetermined place of the wallportion 1 c, a rotation detecting surface 1 d is disposed in closevicinity to the cylindrical portion of the rotor 5.

[0027] Furthermore, in the housing 1, an accommodating portion 1 e isformed. The accommodating portion 1 e accommodates a circuit board 2,which will be explained later, and the magnetic detecting portion 3 thatis a rotation detecting portion, and has a not shown guide groove thatguides and supports the circuit board 2. When the circuit board 2 isguided along the guide groove of the accommodating portion 1 e andaccommodated therein, the magnetic detecting portion 3 is disposed so asto face the rotation detecting surface 1 d. Still furthermore, at anopening end of the housing 1 (lower side of the housing 1 in FIG. 2), asusceptor 1 f for pressure inserting and holding a sealing member 6 thatwill be explained later is formed.

[0028] The circuit board 2 is made of an insulating material such aspaper phenol, glass epoxy or the like, and provided with a not shownwiring pattern thereon. A not shown land portion formed at apredetermined place of the wiring pattern, the magnetic detectingportion 3 and the wiring cord 7 are electrically fixed by use of asolder. After the magnetic detecting portion 3 is disposed in theaccommodating portion 1 e so as to correspond to a position of therotation detecting surface id that is formed in the housing 1, thusformed circuit board 2 is fixed in the accommodating portion 1 e byfilling the sealing member 9 made of such as epoxy or the like in theaccommodating portion 1 e.

[0029] The magnetic detecting portion 3 is made of a magnetic responsiveelement such as a reed switch or the like that detects a change ofmagnetic poles.

[0030] The spacer 4 is provided with an opening 4 a through which theinsertion portion 1 a of the housing 1 is inserted and made of amagnetic member made of metals such as SK, SUM, and SS. The spacer 4 isan annular plane table member in this first embodiment, insertion moldedat a bottom portion 1 g of the housing 1, and disposed so as to surroundthe insertion portion 1 a at the bottom portion 1 g.

[0031] The rotor 5 is provided with a cylindrical portion 5 a that isfitted in the insertion portion 1 a of the housing 1 and capable ofrotating with respect to an outer periphery of the insertion portion 1a, and a rotation transmitter 5 b that matches a locking claw that is arotation biasing portion of a hub of a front wheel that will beexplained later and transmits the rotation of the front wheel to thecylindrical portion 5 a. The cylindrical portion 5 a and the rotationtransmitter 5 b are integrally formed with a plastic magnet made of ananisotropic or isotropic material. For instance, quadrupole magnetizing(800 to 600 gauss) is applied to the cylindrical portion 5 a of therotor 5, and thereby a change of the magnetic poles accompanying therotation of the cylindrical portion 5 a is made detectable by themagnetic detecting portion 3.

[0032] Furthermore, the rotor 5 is disposed in the housing 1 so that,when the cylindrical portion 5 a is fitted into the insertion portion 1a of the housing 1, the rotation transmitter 5 b may be disposed in astate that secures a little distance L from an end portion of theinsertion portion 1 a.

[0033] The sealing member 6 is made of an elastic member such asnitrile, silicone or the like, and is formed into a thin cylinder. Inthe sealing member 6, a groove portion 6 a that is formed into asubstantial V-shape in its cross section is formed over an entirecircumference, and in a thick portion outward from the groove portion 6a a holding member 6 b made of a metal whose cross section is formedinto a substantial L-shape is insertion molded. Such the sealing member6, by forming an outer diameter thereof a little larger than an innerdiameter of a peripheral wall in the susceptor portion 1 f of thehousing 1, can be pressure inserted into the susceptor 1 f of thehousing 1 and held there.

[0034] The wiring cord 7 transmits an output signal from the magneticdetecting portion 3 through the circuit board 2 to the outside, and atan end of the wiring cord 7 a connector portion 7 a for connecting withother instrument is disposed.

[0035] A rotation detector A is formed of the aforementioned respectiveportions. Next, with FIG. 4 added to the above, how to attach therotation detector A to a two-wheeled vehicle will be explained. In thefollowing explanation, coded positions that do not appear in FIG. 4should be referenced to FIGS. 1 to 3.

[0036] In FIG. 4, reference numeral 10 denotes a hub of a front wheel(wheel) 11 of a motorcycle or the like, reference numeral 10 a denotes alocking claw that is a rotation biasing portion for transmitting therotation of the front wheel 11 to the rotation transmitter 5 b of therotor 5, and reference numeral 12 denotes a bearing that is pressureinserted into a concavity 10 b disposed to the hub 10 and provided withan inner wheel 12 a and an outer wheel 12 b, wherein the outer wheel 12b rotates with respect to the inner wheel 12 a with balls 12 ctherebetween. According to the configuration of the above respectiveportions, the front wheel 11 is attached to the axle 13 by means of theinner wheel 12 a of the bearing 12 and disposed rotatably with respectto the axle 13 by means of the outer wheel 12 b.

[0037] In the rotation detector A attached to the front wheel 11configured as mentioned above, the axle 13 is inserted through theinsertion portion 1 a of the housing 1 and the rotation transmitter 5 bdisposed to the rotor 5 is engaged with the locking claw 10 a formed inthe hub 10, and the insertion portion 1 a of the housing 1 is filledinto the hub 10 so as to abut against the inner wheel 12 a of thebearing 12. Thereby, the rotation detector A is fitted between a frontfork 14 and the front wheel 11, thereby the rotor 5 is made rotatableaccompanying the rotation of the front wheel 11.

[0038] Such the rotation detector A is characterized in that the spacer4 that is a magnetic member is disposed at the bottom 1 g of the housing1. The magnetized cylindrical portion 5 a of the rotor 5 is held inclose contact with the bottom portion 1 g owing to the spacer 4 made ofa magnetic material. Accordingly, even when the vibration caused byexternal factors or the like such as an engine displacement and anengine in an idling state in particular when a vehicle is in a stopstate has been transmitted (transmitted through the rotationtransmitting portion 5 b) to the rotor 5, since the rotor 5 is held inclose contact with the spacer 4, the rotor 5 is suppressed fromvibrating, resulting in enabling to hinder a wrong detection in magneticdetection.

[0039] Furthermore, the rotor 5 held in close contact with the bottomportion 1 g of the housing 1 is made possible to maintain a state inwhich the rotation transmitting portion 5 b does not abut against theouter wheel 12 b of the bearing 12 that is disposed to the hub 10. Thisis, because vibration modes transmitted to the rotor 5 are differentfrom each other between the inner wheel 12 a and the outer wheel 12 b ofthe bearing 12, of importance in view of hindering the wrong detectionby the magnetic detecting portion 5 from occurring.

[0040] That is, the outer wheel 12 b of the bearing 12 has the vibrationmode that is transmitted from tires attached to the front wheel 11 andthat is different from that of the rotation detector A attached throughthe insertion portion 1 a to the axle 13. Since two different kinds ofvibration modes are not allowed to transmit to the rotor 5, the wrongdetection in the magnetic detection may be hindered from occurring.

[0041] The wrong detection in the magnetic detection is conspicuouslycaused when the magnetic detecting portion 3 is made of the reed switchand a magnetized area applied to the cylindrical portion 5 a is locatedat a switching point in the rotation detecting surface 1 d of thehousing 1. However, since by intervening the spacer 4 made of a magneticmaterial the rotor 5 may be suppressed from vibrating, even when acheaper magnetic detecting portion where the reed switch is used isused, a rotation detector A that allows excellently detecting therotation can be obtained.

[0042] Next, a modification mode of the first embodiment will beexplained with reference to FIG. 5. For the same or corresponding placesas the first embodiment, the same reference numerals are given and theirdetailed explanations will be omitted.

[0043] In a rotation detector A shown in FIG. 5, there is a differentpoint from the first embodiment in that without disposing the spacer 4made of a magnetic material, rotor 5 is held in close contact with thebottom portion 1 g of the housing 1.

[0044] That is, in the rotation detector A, the insertion portion 1 adisposed in the housing 1 is made of the same material as, for instance,the spacer 4 (metals such as SK, SUM and SS), and by disposing anabutting portion (magnetic member) 1 h, which abuts against thecylindrical portion 5 a of the rotor 5 in the bottom portion 1 g of thehousing 1, to the insertion portion 1 a, similarly to the firstembodiment, the cylindrical portion 5 a of the rotor 5 is held in closecontact with the bottom portion 1 g side of the housing 1.

[0045] In thus configured rotation detector A, by use of the abuttingportion 1 h that is integrally disposed with the insertion portion 1 aand exposed from the bottom portion 1 g of the housing 1, an identicaleffect as the aforementioned spacer 4 is disposed can be obtained. Inaddition, by configuring the abutting portion 1 h that is a magneticmaterial so as to be integrated with the insertion portion 1 a, a partscount may be decreased, resulting in the cost reduction in manufacturingthe rotation detector A.

[0046] Furthermore, in the first embodiment, the spacer 4 is disposed tothe bottom portion 1 g of the housing 1 by means of insertion molding.However, the spacer 4 may be disposed and fixed to the bottom portion 1g of the housing 1 by use of an adhesive or the like.

[0047] Next, a second embodiment will be explained with reference toFIGS. 6 and 7. For the same or corresponding places as the firstembodiment, the same reference numerals are given and their detailedexplanations will be omitted.

[0048] The rotor 5 according to the second embodiment is provided withconvexities 5 d capable of abutting against the inner wheel 12 a atpositions that face the inner wheel 12 a of the bearing 12.

[0049] Four convexities 5 d are partially disposed at places that facethe inner wheel 12 a and along a periphery of an opening 5 c throughwhich the insertion portion 1 a is inserted.

[0050] Furthermore, the rotor 5 is disposed in the housing 1 so thatwhen the cylindrical portion 5 a is filled into the insertion portion 1a of the housing 1, the convexities 5 d may be located at places thatsecure a little distance L from an end portion of the insertion portion1 a.

[0051] In FIG. 7, the inner wheel 12 a of the bearing 12 is fixed in astate where through the axle 13 from right to left in the figure, thehousing 1 (insertion portion 1 a), the inner wheel 12 a, a tubular body11 a inside of the hub 10 of the front wheel 11 and an intermediatetubular body 15 are pinched by the front fork 14. Accordingly, when thehousing 1 equipped with the magnetic detecting portion 3 and the innerwheel 12 a are caused to vibrate, their vibrations become the same one.By contrast, since the outer wheel 12 b of the bearing 12 is fixed tothe hub 10 of the front wheel 11, when the front wheel 11 and the outerwheel 12 b are caused to vibrate, their vibrations become the same one.Since the inner wheel 12 a and the outer wheel 12 b are disposed withthe ball 12 c therebetween, the vibration is not transmitted uniformly.Accordingly, since the vibration mode of the rotation detector Aattached through the insertion portion 1 a to the axle 13 and one thatis transmitted from the tires mounted to the front wheel 11 to the outerwheel 12 b of the bearing 12 are different, when the rotor 5 is broughtinto contact with the outer wheel 12 b that is different in thevibration mode from the magnetic detecting portion 3 that is therotation detecting portion, because of the difference of the vibrationmode, the wrong detection may result. Accordingly, when the rotor 5 isbrought into contact with the inner wheel 12 a that is the same in thevibration mode as the magnetic detecting portion 3, because thevibration modes become the same one, the wrong detection may be hinderedfrom occurring.

[0052] Furthermore, even when owing to excessive vibration the closecontact of the rotor 5 with the bottom portion 1 g of the housing 1 islost and the rotor 5 moves toward the bearing 12, the rotor 5 canmaintain a state in which the rotor 5 abuts against the inner wheel 12 aof the bearing 12 through the convexities 5 d formed to the rotor 5 anddoes not abut against the outer wheel 12 b. This is important, in viewof the vibration modes transmitted to the rotor 5 being differentbetween the inner wheel 12 a and the outer wheel 12 b of the bearing 12,in hindering the wrong detection due to the magnetic detecting portion 5from occurring.

[0053] The wrong detection in the magnetic detection appearsconspicuously when the magnetic detecting portion 3 is made of the reedswitch and the magnetizing area applied to the tubular body 5 a islocated at a switching point in the rotation-detecting surface 1 d ofthe housing 1. However, by intervening the spacer 4 made of the magneticmaterial, the vibration of the rotor 5 can be suppressed. Furthermore,by disposing the convexities 5 d to the rotation transmitting portion 5b, even when the rotor 5 becomes separated from the bottom portion 1 gdue to the excessive vibration, since the rotor 5 (rotation transmittingportion 5 b) is structured not to abut against the outer,wheel 12 b,even when the cheap magnetic detecting portion that uses the reed switchis used, a rotation detector A that allows detecting the rotation withexcellence can be structured.

[0054] Furthermore, in the second embodiment, since the rotor 5 ispulled toward the bottom portion 1 g side of the housing 1, the rotor 5comes rarely into contact with the inner wheel 12 a. However, bysubstituting a corrugated washer for the spacer 4 in the secondembodiment, the corrugated washer may be applied to one in which therotor 5 is pushed toward the bearing 12. In this case also, since therotor 5 comes into connection with the inner wheel 12 a owing to theconvexities 5 d and can be hindered from vibrating, even when the cheapmagnetic detecting portion that uses the reed switch is used, therotation detector A that allows detecting the rotation with excellencecan be structured.

[0055] Next, a modification mode of the second embodiment will beexplained with reference to FIG. 8. For the same or corresponding placesas the second embodiment, the same reference numerals are given andtheir detailed explanations will be omitted.

[0056] The present modification mode is different from the secondembodiment in that similarly to the modification mode of the firstembodiment, without disposing the spacer 4 that is made of the magneticmaterial, the rotor 5 is held in close contact with the bottom portion 1g of the housing 1. By constituting like this, the identical operationaleffect as the modification mode of the first embodiment can be obtained.

[0057] Next, a third embodiment will be explained with reference toFIGS. 9 and 10. For the same or corresponding places as theaforementioned respective embodiments, the same reference numerals aregiven and their detailed explanations will be omitted.

[0058] The rotor 5 in the third embodiment is provided with projections5 e that abut against a side face 10 c that is an opposing place withthe locking claw 10 a (one that abuts against the rotation transmittingportion 5 b and transmits the rotation of the front wheel 11 to therotation transmitting portion 5 b) that is the rotation-biasing portionof the hub 10 of the rotation transmitting portion 5 b. The projections5 e are formed into a semi-sphere that comes into a point contact withthe locking claw 10 a.

[0059] Thus, by disposing the projections 5 e at portions where therotation transmitting portion 5 b of the rotor 5 abuts against thelocking claw 10 a, a contact area between the rotation transmittingportion 5 b and the locking claw 10 a can be made smaller. Accordingly,even when during a stop state of the vehicle, the vibration exerted byan engine in an idling state, external factors and so on is transmitted(transmitted through the rotation transmitting portion 5 b) to the rotor5, the rotor 5 can be held in close contact with the spacer 4 and evenwhen the rotation transmitting portion 5 b in the rotor 5 comes intocontact with the locking claw 10 a, owing to the projections 5 e thecontact area between both members can be maintained smaller.Accordingly, since the vibration can be hindered from transmitting, thewrong detection in the magnetic detection can be hindered fromoccurring.

[0060] The lubricant 8 applied to the housing 1, when the rotor 5rotates, is scattered into a space intimately closed by the housing 1and the sealing member 6 and comes into a portion where the clockingclaw 10 a abuts against the rotation transmitting portion 5 b. In thiscase, when a portion where the rotation transmitting portion 5 b abutsagainst the clocking claw 10 a is in surface contact, the lubricant 8sticks together the rotation transmitting portion 5 b and the clockingclaw 10 a. Accordingly, when the clocking claw 10 a is separating fromthe rotation transmitting portion 5 b owing to the vibration or thelike, it can separate with difficulty. As a result, the rotor 5 isforced to move, resulting in appearing as the detection noise of therotation detector A.

[0061] On the other hand, when the third embodiment is adopted, evenwhen the lubricant 8 comes into the portion where the rotationtransmitting portion 5 b and the clocking claw 10 a abut against eachother, since the clocking claw 10 a and the rotation transmittingportion 5 b abut in a point contact, the lubricant 8 does not stick therotation transmitting portion 5 b and the clocking claw 10 a.Accordingly, owing to the vibration or the like, when the clocking claw10 a is separating from the rotation transmitting portion 5 b, since itcan be easily separated, without moving the rotor 5, the detection noiseof the rotation detector A may be hindered from occurring.

[0062] In the third embodiment, although the projection 5 e is formedinto a hemispherical shape, its shape is not restricted to this one. Anyshape that can make smaller the contact area where the rotationtransmitting portion 5 b and the clocking claw 10 a abut against eachother can be used. For instance, the shape may be one like a wall thatallows coming into line contact. Furthermore, its cross section is notrestricted to being spherical and may be provided with an angle that twostraight lines intersect.

[0063] Furthermore, when the clocking claw 10 a of the hub 10 isprovided with a projection, a place where the rotation transmittingportion 5 b comes into contact may be a flat surface.

[0064] Still furthermore, by providing the rotor 5 made of plasticmagnet with the projections 5 e, the projections 5 e can be madecheaper, resulting in cost reduction.

[0065] Furthermore, the shape of the clocking claw 10 a is notrestricted to the clocking claw 10 a in this third embodiment, but byforming a notch, the rotation transmitting portion 5 b may be allowed tolocate there.

[0066] The wrong detection in the magnetic detection appearsconspicuously when the magnetic detecting portion 3 is made of the reedswitch and the magnetizing area applied onto the cylindrical portion 5 ais located at a switching point in the rotation-detecting surface 1 d ofthe housing 1. However, since the rotor 5 can be hindered from rotatingtogether with the hub 10, even when the cheap magnetic detecting portionthat uses the reed switch is used, the rotation detector A that allowsdetecting the rotation with excellence can be structured.

[0067] Furthermore, in the third embodiment, the spacer 4 is insertionmolded and disposed to the bottom portion 1 g of the housing 1. However,in the invention, the spacer 4 may be disposed and fixed to the bottomportion 1 g of the housing 1 by use of an adhesive or the like.

[0068] Furthermore, in the third embodiment, since the rotor 5 is pulledtoward the bottom portion 1 g side of the housing 1, it comes rarelyinto contact with the inner wheel 12 a. However, the invention may beapplied to one in which by substituting a corrugated washer for thespacer 4 in the aforementioned embodiment, the rotor 5 is pushed towardthe bearing 12. In this case also, since the rotor 5 abuts against theinner wheel 12 a through the convexities 5 d and can be hindered fromvibrating, even when the cheap magnetic detecting portion that uses thereed switch is used, a rotation detector A that allows detecting therotation with excellence can be structured.

[0069] Furthermore, similarly to the aforementioned respectivemodification modes, without disposing the spacer 4 that is made of themagnetic material, the rotor 5 may be held in close contact with thebottom portion 1 g of the housing 1. By constituting like this, theidentical operational effect as the modification modes of theaforementioned respective embodiments can be obtained.

[0070] Still furthermore, in the aforementioned respective embodimentsand modification modes, the rotors 5 in which the cylindrical portion 5a and the rotation transmitting portion 5 b are integrated by use of theplastic magnet were explained. However, the rotor in the invention maybe separately provided with the cylindrical portion 5 a having aplurality of magnetic poles and the rotation transmitting portion 5 bthat transmits the rotation of the wheel to the cylindrical portion 5 a.

[0071] In the aforementioned respective embodiments and modifications,as the rotor 5, one in which the cylindrical portion 5 a having aplurality of magnetic poles and the rotation transmitting portion 5 bthat transmits the rotation of the front wheel 10 to the cylindricalportion 5 a are integrally provided by use of the plastic magnet isused. However, the invention is effective also in a structure of arotation detector based on Japanese Patent Application No. 54850/1999that has been applied by the present applicant, in which an outerperiphery (external surface) of a cylindrical portion of a rotor that isinserted in an insertion portion is provided with concavities andconvexities (gear structure), the rotation of a front wheel istransmitted through a rotation transmitting portion to the concavitiesand convexities, and a magnetic detecting portion that is mainlyconstituted of a magnet and a Hall IC detects the rotating concavitiesand convexities.

Industrial Applicability

[0072] The invention is suitable for a rotation detector that detectsthe rotation number of a wheel of a two-wheeled vehicle.

1. A rotation detector, characterized in comprising a housing providedwith a tubular insertion portion through which an axle is inserted; arotor that is provided with a cylindrical portion through which theinsertion portion is inserted and that has a plurality of magneticpoles, and rotates synchronously with a wheel equipped to the axle; arotation detecting portion that detects a change of the magnetic polesaccompanying rotation of the cylindrical portion; and a magnetic memberthat is disposed in the surroundings of the insertion portion of abottom portion of the housing and capable of holding the rotor at thebottom portion when the cylindrical portion is inserted into theinsertion portion.
 2. A rotation detector as set forth in claim 1,characterized in that the magnetic member is formed of a plane tablemember that is disposed so as to surround the insertion portion in thebottom portion of the housing.
 3. A rotation detector as set forth inclaim 1, characterized in that the magnetic member and the insertionportion are integrally molded.
 4. A rotation detector, characterized incomprising a housing one end of which abuts against an inner wheel of abearing disposed to a hub of a wheel and that is provided with a tubularinsertion portion through which an axle that penetrates through thebearing is inserted; a rotor that is provided with a cylindrical portionthrough which the insertion portion is inserted and a rotationtransmitting portion for rotating the cylindrical portion synchronouslywith the rotation of the wheel; a rotation detecting portion that isdisposed to the housing and detects the rotation of the rotor; and aconvexity that is disposed at a place that faces an inner wheel in thebearing of the rotor and abuttable against the inner wheel.
 5. Arotation detector as set forth in claim 4, characterized in that theconvexity is partially disposed at a place that faces the inner wheeland along a periphery of an opening through which the insertion portionis inserted.
 6. A rotation detector, characterized in comprising ahousing one end of which abuts against a bearing disposed to a hub of awheel and that is provided with a tubular insertion portion throughwhich an axle that penetrates through the bearing is inserted; a rotorthat is provided with a cylindrical portion through which the insertionportion is inserted and a rotation transmitting portion for transmittingrotation of the wheel to the cylindrical portion by abutting against arotation biasing portion disposed to the hub; a rotation detectingportion that is disposed to the housing and detects the rotation of therotor; and a contact portion that is disposed to a portion that abutsagainst the rotation-biasing portion of the rotation transmittingportion and maintains a contact area between both members smaller.
 7. Arotation detector as set forth in claim 6, characterized in that thecontact portion is provided with a projection that comes into contactwith a flat surface of the rotation-biasing portion.
 8. A rotationdetector as set forth in claim 6, characterized in that the contactportion is made of a flat surface that comes into contact with aprojection disposed to the rotation-biasing portion.